Analysis of trials which have investigated the effects of lowering low density lipoprotein (LDL) levels on coronary heart disease (CHD), as determined by changes on quantitative coronary angiography and in the incidence of cardiovascular events, suggests that the percentage decrease in LDL cholesterol provides a better index of outcome than does its absolute level on treatment. Additional data suggest that it may be advantageous to employ therapy which not only lowers LDL cholesterol but also decreases serum triglyceride and/or increases HDL cholesterol. These conclusions have important implications for future guidelines on CHD prevention.